Wednesday, April 18, 2012

Not-quite-so elementary, my dear electron : Nature News: ...in the 1980s, physicists predicted that electrons in a one-dimensional chain of atoms could be split into three quasiparticles: a ‘holon’ carrying the electron’s charge, a ‘spinon’ carrying its spin (an intrinsic quantum property related to magnetism) and an ‘orbiton’ carrying its orbital location.

“These quasiparticles can move with different speeds and even in different directions in the material...” Atomic electrons have this ability because they behave like waves when confined within a material. “When excited, that wave splits into multiple waves, each carrying different characteristics of the electron; but they cannot exist independently outside the material...”

In 1996, physicists split an electron into a holon and spinon. Now, van den Brink and his colleagues have broken an electron into an orbiton and a spinon, as reported in Nature today. The team created the quasiparticles by firing a beam of X-ray photons at a single electron in a one-dimensional sample of strontium cuprate. The beam excited the electron to a higher orbital, causing the beam to lose a fraction of its energy in the process, then rebounded. The team measured the number of scattered photons in the rebounding beam, along with their energy and momentum, and compared this with computer simulations of the beam's properties. The researchers found that when the photons' energy loss was between about 1.5 and 3.5 electronvolts, the beam's spectrum matched their predictions for the case in which an orbiton and spinon had been created and were moving in opposite directions through the material.